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SOUTH JORDAN, Utah (KSTU) — A 67-year-old woman who ordered sweet tea at a Dickey’s Barbecue Pit had to be rushed to a hospital after authorities say she ingested a ‘highly toxic substance.’ Sister station FOX 13 reports the woman’s mouth and throat started to burn within seconds of drinking the tea that had somehow been mixed with a cleaning chemical.

The chemical is used to clean the restaurant’s fryers and is comprised of 67 percent sodium hydroxide, which can be lethal if consumed. Police are still investigating to find out how the tea and chemical got mixed.

“I don’t know how much was put into this drink, but from what I understand it was a highly toxic substance,” South Jordan Officer Sam Winkler said. “Is this something that was stored improperly? Was it an accident? Was it intentional? We really don’t know, that’s why investigators are looking in on this case.”

Sunday night the woman was taken to a hospital close to the restaurant and later flown in a helicopter to the University of Utah’s burn center. Ofc. Winkler said she was still in extremely critical condition as of Wednesday night.

FOX 13 reached out to the franchise owner, Finger Lickin’ Brands, LLC, and was provided a statement from company president John Thomson:

“Our thoughts and prayers go out to our guest and her family. Safety is something we take very seriously when it comes to our valued guests, as well as our own team members. At this time we are fully involved in cooperating with all parties. Out of respect for the privacy of our guest and her family, we will reserve further remarks for the time being.”

The county health department was called to inspect the restaurant and found no existing risk to the public after a routine review.